Ranged weapon firing does not depend on DefaultGrid anymore.

Content.Client/GameObjects/Components/Weapons/Ranged/ClientRangedWeaponComponent.cs

@@ -1,6 +1,7 @@
-using Content.Shared.GameObjects.Components.Weapons.Ranged;
+using Content.Shared.GameObjects.Components.Weapons.Ranged;
 using Robust.Shared.GameObjects;
 using Robust.Shared.Map;
+using Robust.Shared.Maths;
 
 namespace Content.Client.GameObjects.Components.Weapons.Ranged
 {
@@ -30,9 +31,9 @@ namespace Content.Client.GameObjects.Components.Weapons.Ranged
             FireRateSelector = rangedState.FireRateSelector;
         }
 
-        public void SyncFirePos(GridCoordinates worldPos)
+        public void SyncFirePos(GridId targetGrid, Vector2 targetPosition)
         {
-            SendNetworkMessage(new FirePosComponentMessage(worldPos));
+            SendNetworkMessage(new FirePosComponentMessage(targetGrid, targetPosition));
         }
     }
 }

Content.Client/GameObjects/EntitySystems/RangedWeaponSystem.cs

@@ -11,6 +11,7 @@ using Robust.Shared.Input;
 using Robust.Shared.Interfaces.Map;
 using Robust.Shared.Interfaces.Timing;
 using Robust.Shared.IoC;
+using Robust.Shared.Map;
 
 namespace Content.Client.GameObjects.EntitySystems
 {
@@ -96,9 +97,13 @@ namespace Content.Client.GameObjects.EntitySystems
             var worldPos = _eyeManager.ScreenToMap(_inputManager.MouseScreenPosition);
 
             if (!_mapManager.TryFindGridAt(worldPos, out var grid))
-                grid = _mapManager.GetDefaultGrid(worldPos.MapId);
+            {
-
+                weapon.SyncFirePos(GridId.Invalid, worldPos.Position);
-            weapon.SyncFirePos(grid.MapToGrid(worldPos));
+            }
+            else
+            {
+                weapon.SyncFirePos(grid.Index, grid.MapToGrid(worldPos).Position);
+            }
         }
     }
 }

Content.Server/GameObjects/Components/Weapon/Ranged/Barrels/ServerRangedBarrelComponent.cs

@@ -159,10 +159,10 @@ namespace Content.Server.GameObjects.Components.Weapon.Ranged.Barrels
         public override void OnAdd()
         {
             base.OnAdd();
-            var rangedWeapon = Owner.GetComponent<ServerRangedWeaponComponent>();
+            var rangedWeaponComponent = Owner.GetComponent<ServerRangedWeaponComponent>();
-            rangedWeapon.Barrel = this;
+            rangedWeaponComponent.Barrel = this;
-            rangedWeapon.FireHandler += Fire;
+            rangedWeaponComponent.FireHandler += Fire;
-            rangedWeapon.WeaponCanFireHandler += WeaponCanFire;
+            rangedWeaponComponent.WeaponCanFireHandler += WeaponCanFire;
         }
 
         public override void OnRemove()
@@ -208,7 +208,12 @@ namespace Content.Server.GameObjects.Components.Weapon.Ranged.Barrels
             return true;
         }
 
-        private void Fire(IEntity shooter, GridCoordinates target)
+        /// <summary>
+        /// Fires a round of ammo out of the weapon.
+        /// </summary>
+        /// <param name="shooter">Entity that is operating the weapon, usually the player.</param>
+        /// <param name="targetPos">Target position on the map to shoot at.</param>
+        private void Fire(IEntity shooter, Vector2 targetPos)
         {
             var soundSystem = EntitySystem.Get<AudioSystem>();
             if (ShotsLeft == 0)
@@ -229,8 +234,7 @@ namespace Content.Server.GameObjects.Components.Weapon.Ranged.Barrels
             }
 
             // At this point firing is confirmed
-            var worldPosition = IoCManager.Resolve<IMapManager>().GetGrid(target.GridID).LocalToWorld(target).Position;
+            var direction = (targetPos - shooter.Transform.WorldPosition).ToAngle();
-            var direction = (worldPosition - shooter.Transform.WorldPosition).ToAngle();
             var angle = GetRecoilAngle(direction);
             // This should really be client-side but for now we'll just leave it here
             if (shooter.TryGetComponent(out CameraRecoilComponent recoilComponent))

Content.Server/GameObjects/Components/Weapon/Ranged/ServerRangedWeaponComponent.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using Content.Server.GameObjects.Components.GUI;
 using Content.Server.GameObjects.Components.Mobs;
 using Content.Server.GameObjects.Components.Weapon.Ranged.Barrels;
@@ -12,6 +12,7 @@ using Robust.Shared.Audio;
 using Robust.Shared.GameObjects;
 using Robust.Shared.GameObjects.Systems;
 using Robust.Shared.Interfaces.GameObjects;
+using Robust.Shared.Interfaces.Map;
 using Robust.Shared.Interfaces.Network;
 using Robust.Shared.Interfaces.Random;
 using Robust.Shared.Interfaces.Timing;
@@ -19,6 +20,7 @@ using Robust.Shared.IoC;
 using Robust.Shared.Localization;
 using Robust.Shared.Log;
 using Robust.Shared.Map;
+using Robust.Shared.Maths;
 using Robust.Shared.Players;
 using Robust.Shared.Random;
 using Robust.Shared.Serialization;
@@ -38,7 +40,7 @@ namespace Content.Server.GameObjects.Components.Weapon.Ranged
 
         public Func<bool> WeaponCanFireHandler;
         public Func<IEntity, bool> UserCanFireHandler;
-        public Action<IEntity, GridCoordinates> FireHandler;
+        public Action<IEntity, Vector2> FireHandler;
 
         public ServerRangedBarrelComponent Barrel
         {
@@ -77,6 +79,7 @@ namespace Content.Server.GameObjects.Components.Weapon.Ranged
             serializer.DataField(this, p => p.ClumsyExplodeChance, "clumsyExplodeChance", 0.5f);
         }
 
+        /// <inheritdoc />
         public override void HandleNetworkMessage(ComponentMessage message, INetChannel channel, ICommonSession session = null)
         {
             base.HandleNetworkMessage(message, channel, session);
@@ -95,7 +98,24 @@ namespace Content.Server.GameObjects.Components.Weapon.Ranged
                         return;
                     }
 
-                    _tryFire(user, msg.Target);
+                    if (msg.TargetGrid != GridId.Invalid)
+                    {
+                        // grid pos
+                        if (!IoCManager.Resolve<IMapManager>().TryGetGrid(msg.TargetGrid, out var grid))
+                        {
+                            // Client sent us a message with an invalid grid.
+                            break;
+                        }
+
+                        var targetPos = grid.LocalToWorld(msg.TargetPosition);
+                        TryFire(user, targetPos);
+                    }
+                    else
+                    {
+                        // map pos
+                        TryFire(user, msg.TargetPosition);
+                    }
+
                     break;
             }
         }
@@ -105,7 +125,12 @@ namespace Content.Server.GameObjects.Components.Weapon.Ranged
             return new RangedWeaponComponentState(FireRateSelector);
         }
 
-        private void _tryFire(IEntity user, GridCoordinates coordinates)
+        /// <summary>
+        /// Tries to fire a round of ammo out of the weapon.
+        /// </summary>
+        /// <param name="user">Entity that is operating the weapon, usually the player.</param>
+        /// <param name="targetPos">Target position on the map to shoot at.</param>
+        private void TryFire(IEntity user, Vector2 targetPos)
         {
             if (!user.TryGetComponent(out HandsComponent hands) || hands.GetActiveHand?.Owner != Owner)
             {
@@ -158,7 +183,7 @@ namespace Content.Server.GameObjects.Components.Weapon.Ranged
                 return;
             }
 
-            FireHandler?.Invoke(user, coordinates);
+            FireHandler?.Invoke(user, targetPos);
         }
 
         // Probably a better way to do this.

Content.Shared/GameObjects/Components/Weapons/Ranged/SharedRangedWeaponComponent.cs

@@ -1,6 +1,7 @@
-using System;
+using System;
 using Robust.Shared.GameObjects;
 using Robust.Shared.Map;
+using Robust.Shared.Maths;
 using Robust.Shared.Serialization;
 
 namespace Content.Shared.GameObjects.Components.Weapons.Ranged
@@ -26,14 +27,33 @@ namespace Content.Shared.GameObjects.Components.Weapons.Ranged
         }
     }
 
+    /// <summary>
+    /// A component message raised when the weapon is fired at a position on the map.
+    /// </summary>
     [Serializable, NetSerializable]
     public sealed class FirePosComponentMessage : ComponentMessage
     {
-        public GridCoordinates Target { get; }
+        /// <summary>
+        /// If this is not invalid, the target position is relative to the grid.
+        /// Otherwise, it is a map position.
+        /// </summary>
+        public GridId TargetGrid { get; }
 
-        public FirePosComponentMessage(GridCoordinates target)
+        /// <summary>
+        /// If Target Grid is not invalid, this is relative to the grid, otherwise
+        /// it is a map position.
+        /// </summary>
+        public Vector2 TargetPosition { get; }
+
+        /// <summary>
+        /// Constructs a new instance of <see cref="FirePosComponentMessage"/>.
+        /// </summary>
+        /// <param name="targetGrid">The grid that the target position is on, if any.</param>
+        /// <param name="targetPosition">Target position relative to the grid, or a map position if the grid is invalid.</param>
+        public FirePosComponentMessage(GridId targetGrid, Vector2 targetPosition)
         {
-            Target = target;
+            TargetGrid = targetGrid;
+            TargetPosition = targetPosition;
         }
     }
 }